Field of the Invention
The present invention generally relates to an exhaust gas temperature sensor diagnostic system. More specifically, the present invention relates to an exhaust gas temperature sensor diagnostic system capable of running diagnostic during engine startup or shutdown to detect failure of an exhaust gas temperature sensor.
Background Information
Exhaust gas temperature sensors are used to monitor the exhaust gas temperature of an internal combustion engine. By monitoring exhaust gas temperature, the vehicle computer system can estimate the real-time catalyst temperature, and the engine's air-fuel ratio. Conventional exhaust-gas temperature sensor systems can include an exhaust-gas temperature sensor disposed in an exhaust-gas passage of an internal combustion engine, an exhaust-gas temperature measurement unit which obtains an exhaust-gas temperature measurement value on the basis of an output value from the exhaust-gas temperature sensor, and a diagnosis unit which compares an exhaust-gas temperature estimation value to the exhaust-gas temperature measurement value to diagnose exhaust-gas-temperature sensor failure. The exhaust-gas temperature estimation value could come from a model that is based on the ratio of the external heat radiation amount to the exhaust gas heat amount, or other exhaust-gas temperature models.